Pavement marking tapes are typically used to delineate the boundaries for lanes of traffic on a roadway. The tape may extend continuously, such as along the outermost boundaries of the driving lanes, or intermittently, such as between lanes. One popular use for such a tape is in construction work zones, where pavement marking tape can guide motorists through new traffic patterns without incident. Although these work zones may seem to remain in place for inordinately long periods of time, they eventually are removed and the pavement marking is removed from the roadway. To allow the pavement marking tape to be peeled from the surface of the roadway in a single piece, the marking tape must have sufficient structural integrity to prevent tearing. If the tape is intended to remain in place indefinitely, it is necessary to provide structural integrity sufficient to withstand the abuse that vehicles and weather can impose.
Various removable pavement marking tapes have been developed for uses such as that described above, and some such tapes include an integral scrim. An example of such a tape is the 3M Scotch-Lane.TM. Removable Tape sold by the Traffic Control Materials Division of Minnesota Mining and Manufacturing (3M) Company of St. Paul, Minn. under the designation 620. A simplified illustration of this type of conventional tape is provided in FIG. 1. Tape 10 includes a monolayer of glass beads 12 retained by binder layer 14, which is bonded to aluminum layer 16. Glass beads 12 provide retroreflectivity for the headlights of oncoming vehicles, and enable motorists to detect the pavement marking tape more easily than without such beads. Aluminum layer 16 provides deformability, which enables the tape to better adhere over imperfections in the surface of the road.
Beneath the aluminum layer 16 are adhesive layers 18 and 22, which permeate scrim 20 and bond it to the aluminum layer. Scrim 20 is typically a nonwoven sheet of natural staple fibers or synthetic melt-blown or spun-bonded polymeric fibers, or a composite. It may include a plurality of larger strands extending in the machine (longitudinal) direction, the transverse direction, or both to provide added strength and structural integrity. Scrim 20 exhibits good tensile strength, and thus is useful for peeling the tape 10 off road surface 24 to which it is adhesively bonded. The scrim also may help to prevent residual adhesive from remaining bonded to the road surface when the tape has been removed.
Although removable pavement marking tapes of the type described above are useful for many applications, they may exhibit certain disadvantages when applied to existing road surfaces. Those surfaces are usually irregular compared to new roads, and often exhibit topographical defects such as projections, impacted rocks or debris, dents, and the like. Although the aluminum layer alone is susceptible to inelastic deformation, and would otherwise enable the tape to be adhered to an irregular surface, the scrim is not. It is believed that the scrim can prevent this type of pavement marking tape from conforming to irregularities in the road surface, perhaps because the scrim increases the tendency of the tape to recover to its original shape (elasticity) after it has been deformed over a surface irregularity. When the tendency to recover exceeds the adhesive force attaching the tape to the surface, detachment occurs. Moreover, adhesion problems can be exacerbated by the presence of water on the road surface and under the tape which, in conjunction with freeze/thaw cycles, can accelerate the detachment process. Once the tape becomes partially or wholly detached from the road, the advantages offered by the tape, such as retroreflectivity, may no longer be obtained.
In view of these and other disadvantages of conventional pavement marking tapes, it is desirable to provide a pavement marking tape that effectively conforms to irregularities in a road surface and is easily removable in one piece.